Half-hours with the Telescope eBook

Next, let the observer turn towards the south again.
Above Corvus, in the position shown in the Frontispiece,
there are to be seen five stars, forming a sort of
wide V with somewhat bowed legs. At the angle
is the star [gamma] Virginis, a noted double.
In 1756 the components were 6-1/2 seconds apart.
They gradually approached till, in 1836, they could
not be separated by the largest telescopes. Since
then they have been separating, and they are now 4-1/2
seconds apart, situated as shown in Plate 3.
They are nearly equal in magnitude (4), and both pale
yellow.

The star [gamma] Leonis is a closer and more beautiful
double. It will be found above Regulus, and is
the brightest star on the blade of the Sickle.
The components are separated by about 3-1/5 seconds,
the larger of the second, the smaller of the fourth
magnitude; the former yellow-orange, the latter greenish-yellow.

Lastly, the star [iota] Leonis may be tried.
It will be a pretty severe test for our observer’s
telescope, the components being only 2".4 apart, and
the smaller scarcely exceeding the eighth magnitude.
The brighter (fourth magnitude) is pale yellow, the
other light blue.

CHAPTER IV.

A HALF-HOUR WITH BOOTES, SCORPIO, OPHIUCHUS, ETC.

We now commence a series of observations suited to
the third quarter of the year, and to the following
hours:—­Ten o’clock on the 22nd of
July; nine on the 8th of August; eight on the 23rd
of August; seven on the 8th of October; and intermediate
hours on days intermediate to these.

We look first for the Great Bear towards the north-west,
and thence find the Pole-star. Turning towards
the north we see Capella and [beta] Aurigae low down
and slightly towards the left of the exact north point.
The Milky Way crosses the horizon towards the north-north-east
and passes to the opposite point of the compass, attaining
its highest point above the horizon towards east-south-east.
This part of the Milky Way is well worth observing,
being marked by singular variations of brilliancy.
Near Arided (the principal star of Cygnus, and now
lying due east—­some twenty-five degrees
from the zenith) there is seen a straight dark rift,
and near this space is another larger cavity, which
has been termed the northern Coal-sack. The space
between [gamma], [delta], and [beta] Cygni is covered
by a large oval mass, exceedingly rich and brilliant.
The neighbouring branch, extending from [epsilon]
Cygni, is far less conspicuous here, but near Sagitta
becomes brighter than the other, which in this neighbourhood
suddenly loses its brilliancy and fading gradually
beyond this point becomes invisible near [beta] Ophiuchi.
The continuous stream becomes patchy—­in
parts very brilliant—­where it crosses Aquila
and Clypeus. In this neighbourhood the other stream
reappears, passing over a region very rich in stars.
We see now the greatest extent of the Milky Way, towards
this part of its length, ever visible in our latitudes—­just
as in spring we see its greatest extent towards Monoceros
and Argo.